The present invention is, in general, directed to an apparatus and method for monitoring a level of a chemical species in body fluid. More particularly, the present invention relates to a dermal apparatus and method for monitoring the level of a chemical species, such as lactate, in perspiration.
Athletic activities typically involve the contraction and relaxation of muscles at high rates. During such activities, adenosine triphosphate (ATP) is hydrolyzed to adenosine diphosphate (ADP) producing energy for muscle contraction. The body can manufacture ATP from ADP by glucose oxidation to supply energy for continued muscular activity. When the physical or athletic activity is of low exertion, the muscles are well oxygenated and glucose is efficiently oxidized in the presence of ADP to reform ATP. As the physical or athletic performance transitions to greater intensity, oxygen becomes limited and there is a shift to anaerobic glucose oxidation for replenishing ATP. Anaerobic glucose oxidation is less efficient than aerobic oxidation producing only a fraction of ATP.
A byproduct of the anaerobic ATP manufacture is lactate, also known as lactic acid. With high intensity exercise, lactate accumulates in the muscles, for example, in the legs of runners and cyclists and in the arms of rowers. With increased accumulation of lactate, athletic performance levels decline or cease. Simultaneously, the accumulated lactate enters the bloodstream and is expelled through body secretions such as perspiration.
It is often desirable to monitor lactate levels to maximize high intensity athletic performance. By maximizing glucose oxidation efficiency an athlete can save carbohydrates, and thus perform or train longer.
A number of devices have been developed for the determination of lactate and/or other chemical species in perspiration. These devices typically include a collection pad which is attached to the skin of an individual to obtain a desired amount of perspiration. The collection pad is removed from the individual and the collected perspiration is processed to determine the amount of lactate in the perspiration using chemical or electrochemical techniques. These, however, are not practical devices for monitoring the level of lactate during exercise or other physical or athletic activities.
Generally, the present invention relates to an apparatus and method for monitoring the level of a chemical species, such as lactate or glucose, in a body fluid, such as perspiration. In particular, some embodiments of the invention permit the monitoring of the level of the chemical species during activities, such as exercise or other physical or athletic exertions. One embodiment of the invention is an apparatus for monitoring a level of a chemical species in a body fluid. The apparatus includes a fluid collection layer adapted for receiving the body fluid. The fluid collection layer is dry prior to being brought into contact with the body fluid. A catalyst is provided in, on, or near the fluid collection layer so as to be in contact with the body fluid in the fluid collection layer. The catalyst facilitates a reaction of the chemical species in the body fluid. An indicator, responsive to the reaction of the chemical species, is also provided in, on, or near the fluid collection layer. A characteristic of the indicator changes in response to the reaction of the chemical species, thereby indicating the level of the chemical species in the body fluid.
Another embodiment of the invention is an apparatus for monitoring a level of lactate in perspiration. The apparatus includes a base layer, a reaction layer, an indicator layer, and a cover layer. The base layer is adapted for placement on an animal, preferably on the skin. The reaction layer is positioned over the base layer and includes an enzyme for catalyzing a reaction of lactate in the perspiration to form a product compound. The indicator layer is positioned over the reaction layer and includes an indicator responsive to the product compound. A characteristic of the indicator, such as color, changes in the presence of the product compound. The cover layer is positioned over the indicator layer and has a window for viewing the underlying indicator layer. The reaction layer and indicator layer are dry prior to being brought into contact with the perspiration.
Yet another embodiment is an apparatus for monitoring a level of a chemical species in a body fluid. The apparatus includes a fibrous substrate adapted for collecting the body fluid, a catalyst, and an indicator. The catalyst is disposed proximate to the fibrous substrate so as to be in contact with the body fluid in the fibrous substrate to facilitate a reaction of the chemical species in the body fluid. The indicator is disposed proximate to the fibrous substrate so as to be responsive to the reaction of the chemical species. A characteristic of the indicator changes in response to the reaction of the chemical species, thereby indicating the level of the chemical species.
A further embodiment of the invention is a method for monitoring a level of a chemical species in a body fluid. A monitoring device, responsive to the chemical species, is applied to an animal, preferably on the skin. The device has an absorbent substrate, a catalyst disposed proximately to the substrate, and an indicator disposed proximately to the substrate. The absorbent substrate is dry prior to being brought into contact with the body fluid. Body fluid is received in the fibrous substrate where a chemical species in the body fluid is reacted in the presence of the catalyst. A characteristic of the indicator is then altered in response to the reaction of the chemical species.